# #打印 1-10
# for i in range(1, 11):
#     print(i)

# #打印 10-1
# for i in range(2, 12, 2):
#     print(i)

# #打印 10-1
# for i in range(10, 0, -1):
#     print(i)

sum = 0
for i in range(1, 101):
    sum += i
print(sum)